Canine Degenerative Myelopathy (DM), also known as Chronic Degenerative Radiculomyelopathy (CDRM), is currently an incurable, progressive disease of the canine spinal cord that mimics the symptoms of ALS and/or MS.
Onset is typically after the age of 6 years with an average age of 8 years and older. It is seen most frequently in the German Shepherd Dog, Pembroke Welsh Corgi, and Boxer dog, though the disorder is apparently associated with a gene mutation in SOD1 that has been found in 70 breeds as of 2012, including the Wire Fox Terrier, Chesapeake Bay Retriever, Rhodesian Ridgeback, and Cardigan Welsh Corgi.
Progressive weakness and in coordination of the rear limbs are often the first signs seen in affected dogs, with progression over time to complete flaccid paralysis of the rear, and eventually, front legs. Bladder and Bowel issues are common.
Myelin is an insulating sheath around neurons in the spinal cord. One proposed cause of Degenerative Myelopathy is that the immune system attacks this sheath, breaking it down. This results in a loss of communication between nerves in lower body of the animal and the brain.
The etiology of this disease is unknown. Research has shown that a mutation in the SOD1 gene is a risk factor for developing degenerative myelopathy in several breeds. Mutations in SOD1 are also associated with familial Amyotrophic Lateral Sclerosis, ALS, (Lou Gehrig's disease) in people. Known causes of spinal cord dysfunction should be excluded before accepting the diagnosis of degenerative myelopathy; disc disease (protrusions) or spinal cord tumors can cause compression of the spinal cord with similar signs to degenerative myelopathy.
Though controversy exists, there is also evidence to suggest some breeds may get a form of the disease very similar to a rare form of Multiple Sclerosis, known as Primary Progressive Multiple Sclerosis. In the former DM Flash Test, an Alelle 1101J was implicated in DM of the German Shepherd Dog and this gene is associated with PPMS in humans. Clearly more research is needed to uncover the unknowns surrounding the disease.
Degenerative Myelopathy initially affects the back legs and causes muscle weakness and loss, and lack of coordination. These cause a staggering affect that may appear to be arthritis. The dog may drag one or both rear paws when it walks. This dragging can cause the nails of one foot to be worn down. The condition may lead to extensive paralysis of the back legs.
As the disease progresses, the animal may display symptoms such as incontinence and has considerable difficulties with both balance and walking. If allowed to progress, the animal will show front limb involvement and extensive muscle atrophy and paralysis. Eventually cranial nerve or respiratory muscle involvement necessitates euthanasia or long term palliative care.
Progression of the disease is generally slow but can vary slightly from dog to dog.
x Progressive weakness of the hind
x Worn nails
x Difficulty rising
x Knuckling of the toes
x Scuffing hind feet
x Wearing of the inner digits of the
x Loss of muscle in the rear legs
x Tremors of the rear legs
x Persistent early stages
x Urinary and fecal incontinence
x Eventual front leg weakness from
x Mental stress anxiety
x Pressure sores on boney
x Inability to rise
x Muscle atrophy
x Poor hygiene- soiled appearance
x Organ failure
Immediate veterinary assistance needed regardless of the disease
x Difficulty breathing
x Prolonged seizures
x Uncontrollable vomiting/diarrhea
x Sudden collapse
x Profuse bleeding – internal or external
x Crying/whining from pain*
* If your pet vocalizes due to pain
or anxiety, please consult with your
tending veterinarian immediately
Sadly at this time, there is still no test to confirm DM in a living dog. DM can only be a confirmed diagnosis by having a necropsy performed after a dog has passed. DM is therefore classed as a 'Diagnosis of Exclusion'.
A series of tests, known as 'Rule Out Testing' is recommended if possible, to rule out the many other diseases and conditions that can have the same or similar symptoms as DM. If nothing conclusive is found from this testing, you will be left with what is known as a 'Presumptive Diagnosis of Exclusion.
Recommended Tests to help 'Rule Out' other conditions:
- DM DNA test
- Blood tests to include a full Tick Borne panel to include Lyme disease
- A short course of Steroids (to see if any improvement as this would be indicative of another issue and probably not DM)
- CSF analysis (spinal tap/lumber puncture)
The Orthopedic Foundation for Animals has a DNA saliva test to screen for the mutated gene that has been seen in dogs with Degenerative Myelopathy. The test is only recommended for predisposed breeds, but can be performed on DNA from any dog on samples collected through swabbing the inside of the animal's cheek with a sterile cotton swab or through venipuncture.
The test determines whether the mutated copy of SOD1 is present in the DNA sample submitted. It must be interpreted with caution by a veterinary clinician in combination with the animal's clinical signs and other lab test results.
The DM DNA test is now available from many Testing labs around the world.
The results reported are:• Normal / Normal (N/N, or 'clear'): The dog does not have the mutation and is extremely unlikely to develop Degenerative Myelopathy. There have been cases in which dogs that tested clear were found to have DM upon necropsy. This information was given to Dr Keller from the OFA. Dr Coates performed necropsy. It is important to note the OFA statement on their website that states "Recent evidence suggest that there are other causes of DM in some breeds".
• Normal / Abnormal (N/A or 'carrier'): The dog has one mutated copy of the gene (is heterozygous) and is a carrier but will not have degenerative myelopathy though there has now been several cases of Carriers developing DM. It will be possible for it to pass the mutation to offspring. A thorough examination of the dog's pedigree and DNA testing should be undertaken prior to breeding a dog with this result.
• Abnormal / Abnormal (A/A or 'at risk/ affected'): The dog has two copies (is homozygous) for the mutation and is at risk for Degenerative Myelopathy.
There was a former test known as the DM Flash Test which looked for a change in Allele 1101J. Due to lack of funding the Flash Test is no longer available. It was designed specifically for the German Shepherd breed. Unless more research exists, the Flash Test may never exist again.
Breeding risks for Degenerative Myelopathy can be calculated using the Punnett Square:
If both parents are clear (N/N) then all of the puppies will be clear
- If one parent is a carrier (N/A) and one is clear (N/N) then roughly 50% of the puppies will be clear and 50% will be carriers
- If both parents are carriers (N/A) then roughly 25% will be clear (N/N), 50% will be carriers (N/A), and 25% will be affected (A/A)
- If one parent is clear (N/N) and one parent is affected (A/A) then all puppies will be carriers (N/A)
- If one parent is a carrier (N/A) and one is affected (A/A) then roughly 50% of the puppies will be carriers (N/A) and 50% will be affected (A/A)
- If both parents are affected (A/A) then all puppies will be affected (A/A)
A Punnett Square, for determining potential outcomes of various DNA test results, based on the OFA DM DNA test, can be found here: http://1drv.ms/1S1FomK
Pembroke Welsh Corgi
Hybrid Dog ***
German Shepherd Dog
Cardigan Welsh Corgi
Kerry Blue Terrier
Bernese Mountain Dog
Chesapeake Bay Retriever
*** A hybrid dog is not a BREED; it is a hybrid, which means it is a mix of more than one purebred dog.
also know as Designer Dogs or Boutique Dogs
Statistics from the Orthopedic Foundation for Animals. Evaluations through December 2012
Degenerative Myelopathy is an irreversible, progressive disease that cannot be cured. There are no treatments that have been clearly shown to stop or slow progression of DM though Aminocaproic Acid and NAC have been used with some success to slow down the progression of the disease when started early enough into the disease. Evidence is anecdotal, but some have reported a slowing of progression and a rare few have gone into a type of remission with the use of those two medications along with vitamin supplementation and homemade diets. Speak with your vet about what course to take in treating your dog. The protocol can be found in the helpful links section under Publications. The protocol was designed for the form of DM that most often strikes the German Shepherd Dog.
Exercise has been recommended to maintain the dog's ability to walk. Physiotherapy may prolong the length of time that the dog remains mobile and increase survival time.
Canine hydrotherapy (swimming) may be more useful than walking.
Use of a belly sling or hand-held harness allows the handler the ability to support the dog's hind legs for exercising or going up and down stairs. A supportive harness that cradles the entire pelvis is recommended. "towel walking" can put pressure on the bladder and internal organs.
A 2-wheel dog cart, or "dog wheelchair" can allow the dog to remain active and maintain its quality of life once signs of weakness or paralysis of the hind limbs is detected.